Hexagonal rod die construction having an inherent die surface lubrication system

ABSTRACT

A DIE CONSTRUCTION COMPRISING INCREMENTAL RODS ARRANGED IN REGISTRY, THE ENDS OF THE RODS FORMING INCREMENTAL DIE SURFACE AREAS, SAID RODS BEING MACHINED INDIVIDUALLY PRIOR TO ASSEMBLY WITH A PREDETERMINED LENGTH AND WITH END SURFACES HAVING SURFACE NORMALS SITUATED IN PRECALIBRATED DIRECTIONS, THE MACHINING PROCEDURE INCLUDING THE REMOVAL OF METAL FROM SELECTED RODS TO PROVIDE FLUID FLOW PASSAGES WHICH COMMUNICATE EITHER WITH A LUBRICATION SUPPLY MANIFOLD WHEREBY LUBRICANT IS SELECTIVELY DISTRIBUTED TO SELECTED REGIONS OF THE DIE SURFACE OR WITH AN AIR VENT SPACE WHEREBY AIR ENTRAPPED BY THE WORKPIECE MAY BE VENTED.

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United States Patent Office Patented Mar. 2, 1971 3,566,642 HEXAGONAL ROD DIE CONSTRUCTION HAVING AN INHERENT DIE SURFACE LUBRICATION SYSTEM Foster E. Whitacre, Farmington, Mich., assignor to Ford Motor Company, Dearborn, Mich. Filed Sept. 18, 1968, Ser. No. 760,642 Int. Cl. B21d 37/18 U.S. CI. 7244 5 Claims ABSTRACT OF THE DISCLOSURE A die construction comprising incremental rods arranged in registry, the ends of the rods forming incremental die surface areas, said rods being machined individually prior to assembly with a predetermined length and with end surfaces having surface normals situated in precalibrated directions, the machining procedure including the removal of metal from selected rods to provide fluid flow passages which communicate either with a lubrication supply manifold whereby lubricant is selectively distributed to selected regions of the die surface or with an air vent space whereby air entrapped by the workpiece may be vented.

GENERAL DESCRIPTION OF THE INVENTION My invention relates generally to incremental metal forming dies, but it may be applied as well to other types of dies.

An incremental die construction capable of embodying the improvements of my invention having a pair of die sections, each die section comprising incremental rods, preferably of hexagonal shape, which are arranged in registry. Such a die is described in copending application Ser. No. 749,685, filed Aug. 8, 1968 which is assigned to the assignee of this invention. Reference may be had to that copending application for the purpose of supplementing this disclosure.

Each of the rod increments of each die section of the construction of my invention is machined in a numerically controlled and automated machining procedure. Each rod has a discrete length and is cut into two segments to provide rod end surfaces which form increments of a rough surface equivalent of a finished die surface. Each incremental area has a discrete normal vector direction. One of the rod segments cut from each rod forms a part of the assembly of one die section and the companion rod segment forms an element of the other die section. The surfaces for the companion rod segments are arranged in juxtaposition in precise registry.

The surfaces defined by the incremental end areas of the rods engage the sheet metal in a metal forming die, a concave region of the die surface of one die section complementing the convex region of the companion die section. As the dies are brought into registry, the sheet metal formed at selected regions of the die surface contour must be drawn and stretched, whereas at other regions relatively little metal deformation occurs.

It is desirable to lubricate the surface regions that cause the greatest metal displacement. This is done by machining a chamfer on the corner of selected rods in the die sections and by forming chamfers on the ends of the rod opposite to the ends that define the die surface. Lubricant can be distributed to the passages defined by these chamfers, which lubricant ultimately reaches the surface of the die that engages the blank. The supply of lubricant can be continuous, or it can be supplied in synchronism with the metal forming motion of the die sections.

The chamfers of the individual rod can be carried out in the same numerically controlled and automated machining procedure that is used in the manufacture of the rod segments themselves.

In some circumstances the matching die sections will create regions that entrap air. This makes it necessary to provide air vents in the die sections to accommodate the transfer of air from such regions as the die sections are advanced into registry in the metal forming operation. The same basic procedure used for establishing lubrication passages can be used as well to establish air vent passages. The locations for the vent passages or the lubrication passages, as appropriate, are selected and introduced into the automatic, numerically controlled program as will be explained subsequently, thereby permitting chamfering of the rod segments.

If it is desired to provide so-called knock-out elements in the die sections to remove the formed sheet metal workpiece, certain rods can be removed from the appropriate die sections to rovide an opening in which the knock-out element is received. Special machining of the rods that define the opening thus created is required. This machining can be carried out in the same manner as the machining required to create the chamfer that develops the air vent passages or the lubrication oil flow passages.

BRIEF DESCRIPTION OF THE FIGURES OF THE DRAWINGS FIG. 1 shows in isometric, schematic form a die section in the form of a punch in a metal forming die assembly, the body of the section being formed of incremental rods.

FIG. 1A is an enlargement of section 1A of FIG. 1.

FIG. 2 shows a metal forming die section having openings therein which might accommodate sheet metal blank knockout elements, such as hydraulically actuated knock-out pistons.

FIG. 3 shows a die section, such as that illustrated in FIG. 2, arranged in registry with a companion die section with the sheet metal workpiece located between them, the companion die section having vent holes that permit the escape of entrapped air between the surface of the upper die section and the formed sheet metal workpiece.

FIG. 4 shows in schematic form a pair of die assemblies in which lubrication passages have been formed.

FIGS. 4A, 4B, 4C, and 4D are enlargements of sections 4A, 4B, 4C, and 4D, respectively, of FIGS. 4 and 4C.

FIGS. 5A, 5B and 5C show in diagrammatic form the process steps followed in machining the incremental rods used in making the cooperating die sections.

PARTICULAR DESCRIPTION OF THE INVENTION In FIG. 1 a die section shown at 10 is formed with a convex die surface 12. The body of the die is comprised of hexagonal rod elements 14.

The rods 14 are formed with a predetermined length, the length being determined by the position of the rods in the final assembly. The ends of the rods define incremental areas of the die surface 12.

The hexagonal bar stock of which the rods 14 are formed is machined to a predetermined, discrete length, and it is then cut into two pieces. One of these pieces is used as an increment of the die section 10 and a companion piece is used to form an increment of the other die section with which the section 10 cooperates. The rod increments that are formed from a common piece of bar stock are aligned, and the end surface formed by the cutting operation are arranged in precise registry. The angle at which each end surface is cut and the angular position in space of the rod itself during the cutting operation are predetermined in the programming procedure for the numerical control system.

The rods 14 are bonded together by a suitable bonding operation, such as brazing, after which the rough surface equivalent formed by the end surfaces of the rods 14 can be finished machined.

FIG. 2 shows in isometric form a die section that is a companion to the die section shown in FIG. 1. Like the die section of FIG. 1, the die section of FIG. 2 is formed of incremental, hexagonal rods 16 which are cut during the same cutting operation in which the segments 14 are formed. The length of the segments 14 and 16 are predetermined; and the angle of the cut, as explained previously, also is predetermined. The ends of the rods 16 form an increment of the rough surface of the die section as seen at 18. I

After the rods 16 are assembled and bonded together to form an integral assembly, the assembly can be finished machined to form finished surface 18. Certain rod segments 16 can be removed to provide knock-out pistons and rollers. Such openings are illustrated in FIG. 2, one such opening being identified by reference character 20.

The die sections shown in FIGS. 1 and 2 may be inserted in a suitable housing or binder. The ends of the sheet metal blank are clamped by the binder prior to the instant that the dies are advanced into registry, thereby holding the blank at its margins during the metal forming operation. In these circumstances, the sheet metal is drawn and formed to conform to the surface contour of the die sections.

FIG. 3 shows the die section of FIG. 1 and the die section of FIG. 2 in mutual registry with the sheet metal workpiece 22 and the surface 12 of the die section 10. These openings can be formed by chamfering the corners of the selected hexagonal rods as indicated by the enlarged detailed view of FIG. 1. The chamfer can extend for the length of the rod, thereby providing a through passage extending from the surface of the die. One corner of each of the three cooperating or adjacent hexagonal rods can be chamfered as indicated in FIG. 1. In the alternative, only one corner of one of the three rods shown in FIG. 1 can be chamfered. This also would produce a vent opening although its size would be diminished in comparison to the opening of the dies shown in FIG. 1.

FIG. 4 shows in schematic form a pair of die sections in which provision is made for passage of lubricant through the die. This permits the establishment of a lubrication oil film between the sheet metal worqpiece and the surface of the die. In this instance the lubrication oil passages are formed in the upper die section shown at 38. The companion lower die section 40 is formed with a concave die surface contour that registers with the convex die surface contour of the section 38. The die section 38 is housed within an appropriate binder 42 which cooperates with binder 44 for the lower die section 40. The sheet metal stock 46 is retained by the binder as the die sections 38 and 40 are advanced into registry with each other.

The enlarged portion of the sectional view of FIG. 1 which is enclosed within reference circle A shows a hexagonal rod 48 having one corner chamfered to provide a flat 50. This flat extends through the length of the rod, thereby providing a through passage which will permit distribution of lubricant from the upper region of the die section 38 to the upper surface of the workpiece 46. The impingement of lubricant upon the upper surface of the workpiece is illustrated in the enlarged sectional view enclosed within the reference circle B in FIG. 4. The through passages for lubricating oil are formed in the die section 38 only in those regions that require lubrication during the metal forming operation.

The special machining of the selected rod segments takes place during the same machining process in which the incremental rods themselves are machined and assem- 4 bled. The process steps are illustrated in FIGS. 5A, 5B and 5C. The various machining steps take place in thirteen separate stations. Each station is identified in the drawings by roman numeral reference characters. Certain stations have various substations, each of which is identified by reference numbers.

In Station I, Substation 1, the hexagonal rod bar stock is presented through a turret. At this stage the rod selection is determined by programmed information. If ma terial of varying hardness or chemical characteristics is needed in any particular zone on the finished die, the appropriate material is selected at this stage.

In Station I, Substation 2, the turret is rotated so that the proper bar is presented to the cut-off tools. In Substation 3 the raw bar stock is squared off by a cutting tool after the stock is brought into engagement with a fixed stop. The cut-off blade squares off the end of the rod as indicated in Substation 4. The tail stock shown in Substation 5 is adjusted at this time to the proper X-axis position, and then the stock is fed into the tailstock. The X-axis position is determined by the length of the rod that is required.

In Substation 7 the bar is cut :to produce a rod of precise length. This rod then is transferred to Station II where the rod is automatically clamped into position against an end stop as two milling cutters simultaneously pass across each end. This generates a flat as shown in FIG. 5A. One of the milling cutters is adjustable in an Xaxis direction to accommodate rods of varying length. The machined flats provide a convenient area for impressing stamped identification numbers on the rods. The stamping occurs in Station III, Substation 1. The marking heads are advanced into the rod ends after the rod is fixed against a stop. If it is desired to chamfer the ends of the rods to produce lubrication fiow passages, this is done in Station III, Substation 2. Flow passages similar to that shown in FIG. 4 within reference circle C are made during the final assembly when the rods are chamfered in this fashion.

To produce an axial flow passage for the lubricant, such as that illustrated in FIG. 4, a selected rod is cut with a face mill as indicated in Station IV. This is done after the rod is transferred to Station IV and clamped in a collet chuck. The collet chuck is rotated about its A- axis to some specific angular position so that the proper corner on the X-rod is presented to the milling cutter. Those rods that do not require this special machining bypass this station.

In Station V the rod is transferred to a collet chuck and oriented angularly with respect to the A-axis. It then is positioned in the X-axis direction as indicated in Substation 3. This is done as the cut-off blade is adjusted to the proper angular position as shown in Substation 2. In Substation 4 the cutting operation as illustrated thereby produces two hexagonal rod components, the bases of the rods being complementary to each other.

The cut rod pieces are wire brushed in Station VI to remove any burrs created by the cut-off blade. After this operation the pieces are automatically loaded onto a conveyor and passed to Station VII and then to Station VIII for degreasing and metallic grit blasting.

Copper is sprayed on the rods in the next Station IX. If it is desired to remove one of the rods, certain faces of the rods must be sprayed with a stop-off material that will prevent the application of copper at that region. Removal of some of the rods would be required, for example, if an opening, such as that shown at 20 in FIG. 2, is to be made. The selection of copper or stop-off material, like the other selections necessary throughout the procedure, is made in response to programmed data. If any particular region of the die does not require openings through the punch or die sections, stop-off material is not applied.

In Stations X and XI the rods are automatically oriented into position so that they will present to a reading head the face that is impressed with an identification number in Station III. The reading head identifies the pieces. The odd numbered pieces will be channeled in one direction, and the even numbered pieces will be channeled in another direction. The two groups of rods then are assembled as indicated in Stations XII and XIII. All odd numbered pieces are fed into a fixture whose length, width and depth are adequate for the particular die half involved. The even numbered pieces are assembled in another fixture. The pieces are arranged in numerical order with all of the identified pages oriented in a common direction.

Although I have shown lubrication passages in FIG. 4 only in the upper die section 38, similar passages can be formed in lower die section 40 by using the same numerically controlled and automated procedure for the rods.

The lubricant can be applied under pressure, or it can flow under gravity depending upon the particular requirements.

Having thus described a preferred form of my invention, what I claim and desire to secure by United States Letters Patent is:

1. A metal workpiece forming die section comprising a plurality of rods having a geometric cross section that permits their assembly in close registry, each rod being machined to a predetermined length with the end surface thereof being situated in a plane having a surface normal in a discrete, predetermined direction, the end surfaces of said rods being contiguous and forming incremental areas of a surface of a rough machined casting equivalent, said surface bearing an arbitrary, continuous contour a companion die section having a surface contour that conforms to the surface of the rough machined casting equivalent, selected rods of at least one die section being chamfered to produce passages extending from the surface thereof, said rods being bonded together to form a unitary assembly, the passages formed by said chamfered rods accommodating the flow of fluid through the associated die section.

2. The combination as set forth in claim 1 wherein said passages are adapted to accommodate the flow of lubricant from one region of said associated die section to its surface whereby a lubrication oil film is established between the workpiece and said surface at selected locations.

3. A method for forming a metal forming die comprising the selection of hexagonal bar stock, cutting said bar stock to a predetermined length, cutting the cut bars into two pieces to produce two end surfaces, said end surfaces being contiguous and defining incremental areas of a continuous die surface with a predetermined, arbitrary surface contour, cutting selected rods to form passages extending in the direction of the axis of said rod,

assembling said out pieces into two separate die sections, one piece forming an increment for one die section and the companion rod piece forming a complementary increment for the other die section, said passages forming a through fluid flow path through said one die section, thereby permitting transfer of fluid through said one die section, said passage being in communication with the surface of a workpiece as said die section is brought into engagement therewith.

4. The combination as set forth in claim 3 wherein said passages form a lubrication oil flow path extending from one region of said assembly to the surface of the workpiece that is engaged by said die section.

5. The combination as set forth in claim 3 wherein said passages form an air vent path extending from the region between the workpiece and the adjacent surface of the associated die section.

References Cited UNITED STATES PATENTS 1,336,388 4/1920 Youngberg 72-475 2,332,360 10/1943 Wakefield 76-107 2,490,343 12/ 1949 Fife 72-45 3,277,535 10/1966 Rupert 1844 LOWELL A. LARSON, Primary Examiner US. Cl. X.R. 

